Snap switch



Aug. 28, 195 1 A. V'AN RYAN EIIAL SNAP SIITCH i 2 m t T Q m mm. M A, 3 I t v m 0 u..|\\ 4 i w P ia 0 w 9!..- Z g v w Filed Sept. 27, 1948 ,wzarzzey Patented Aug. 28, 1951 SNAP SWITCH Anthony Van Ryan, South Milwaukee, and William R. Harry, Milwaukee, Wis., assignors to McGraw Electric Company, a corporation of Delaware Application September 2'1, 1948, Serial No. 51,374

Claims.

This invention relates to snap switches and is particularly directed to a sensitive type of switch which requires a small amount of work to actuate it, and whose moving elements are of light weight to thereby secure rapid separation of the contacts.

In switches of this general type, as heretofore constructed, certain material defects exist. One of the principal defects is that as motion is applied to actuate the switch, the force which maintains the movable contact against the stationary contact is progressively reduced and approaches zero just before the contact members separate. This is a serious problem in applications where either the entire switch body is subjected to vibration or where the motion employed to actuate the switch contains a vibratory component. In either of these cases, the contacts will chatter and burning of the contacts will result. These defects become very pronounced where the motion employed to actuate the switch is a slow motion.

This invention is designed to overcome the above noted defects and objects of this invention are to provide a snap switch in which the contact pressure is maintained up to the instant that the switch operates and is not lessened during the motion of its actuating member until the exact instant that the switch snaps to its other position, and to thereby provide a snap switch in which chattering and burning of the contacts will not result, though the s 'tch be subjected to vibration or though the actuating member be moved by a force having a vibratory component.

Embodiments of the invention are shown in the accompanying drawings, in which:

Figure 1 is a plan view of one form of snap switch, such view being partly broken away.

Figure 2 is a side elevation partly in section showing the switch in its uppermost position.

Figure 3 is a view corresponding to Figure 2 showing the switch in its lowermost position.

Figure 4 is a plan view partly broken away of a further form of snap switch of the self-restoring type.

Figures 5 and 6 are side elevations partly broken away showing the switch of Figure 4 in its uppermost and lowermost position, respectively.

Figure 7 is a plan view of a further form of switch which is particularly adapted for a small motion of the actuating member.

Figure 8 is a side elevation of the switch shown in Figure 7.

Figure 9 is a p view of a further form of switch with parts broken away.

Figure 10 is a sectional view taken approximately on the line 10-10 of Figure 9.

Figure 11 is a work diagram.

Referring to Figures 1, 2, and 3 of the drawings, it will be seen that the switch comprises a body portion 1 of insulating material which has a pair of integral bearing members 2 formed of metal and secured to the base I in any suitable manner as by means of the screw 3. If desired, the bearing members may be seated within a slot 4 formed in the base I. It is preferable to cut out the central portion of the bearing members 2, 2 as indicated at 5. These bearing members 2 are provided with transverse slots 6 and I on opposite sides thereof.

The movable portion of the switch is formed of a single piece of spring metal and comprises a centrally located tension member 8 which is joined to a rear portion 9 and a forward portion in. The portion In is relatively wide and is provided with a narrow extension II which constitutes a cantilever type of spring. The portions 9 and I0 may be considered yoke portions. A pair of arms l2 extend inwardly from the yoke portions in and have their inner edges seated within the grooves I of the bearing members 2. It is preferable to stiffen the arms I! by means of channel-like depressions l3. These arms l2, therefore, may be considered relatively rigid arms. A pair of spring arms l4 extend inwardly from the rear yoke portion 9 and have their inner ends seated within the notches 6 of the bearin members 2. These spring arms I! are bowed as shown in Figure 2. The yoke portion 9 is provided with contacts l5 which are adapted to engage either the upper stationary contact 16 or the lower stationary contact H, as shown in Figures 2 and 3.

An upper and a lower stop 18 and i9 are provided for the forward yoke portion ID to thus limit the motion of this part of the switch.

Any suitable operating means may be employed for operating the switch. For the sake of illustration, an upper and :a lower plunger 20 and 2| have been shown.

The operation of the switch is as follows:

Assume that the upper plunger 20 moves downwardly. It is apparent that energy is stored in the cantilever spring or projecting portion I l and there is no lessening of contact pressurevbetween the movable contact l5 and the stationary contact It as long as the yoke portion in remains in contact with its upper stop l8. When the pressure downwardly. due to the deflection of the cantilever spring ll, reaches such a value as to move the yoke 10 away from its upper stop 18,

the yoke in will instantly snap to its lower position against stop I! thereby suddenly causing the switch to instantly snap to its lower position as shown in Figure 3, the pressure between the movable contact I6 and the upper stationary contact I6 remaining at its maximum value up to the instant that the snap-over occurs.

It is apparent that this snap-over will be very quick indeed for the force required to move the movable contact I! away from the upper stationary contact l6 decreases immediately on motion of the movable contact l away from the'upper stationary contact I6. Obviously, the reverse action takes place when the plunger 2| moves upwardly from the position shown in Figure 3. In

exactly the same way the contact pressure between the movable contact l5 and the lower stationary contact I! remains at maximum value up to the instant of snap-over of yoke Ill.

The switch illustrated in Figures 1, 2, and 3 is a non-self-restoring switch. It is obvious, however, that it could be made a self-restoring type of switch by positioning the notch 6 at a higher point than the notch 1, as shown for example for the form of switch illustrated in Figures 4, 5, and 6.

Referring to Figures 4, 5, and 6, a diiferent type of switch has been shown. In this type of switch the notches 22 and 23 are not on the same level, the notch 22 being at a higher point than the notch 23. Only a single upper plunger is required to operate this switch for the switch is, as stated, self-restoring. Other than these two differences, namely, the relative positioning of the notches 22 and 23 and the use of a single plunger, the construction is the same as that shown in Figures 1, 2, and 3 and similar parts are referred to by similar reference characters except ,ior the bearing members 2.

The operation of the switch shown in Figures 4, 5, and 6 for the down stroke is as follows:

When the plunger moves downwardly it stores energy in the cantilever spring or arm II and deflects such arm downwardly. When a suiiicient force is exerted by the spring II the yoke in leaves its upper stop is and the switch snaps from the position shown in Figure 5 to thatshown in Figure 6. However, there is no lessening of pressure between the movable contact l5 and the upper stationary contact l6 until at the exact instant that the snap-over of the yoke l0 occurs. When the plunger 20 moves upwardly the pressure exerted by the cantilever spring ll decreases and as soon as the yoke I6 moves upwardly from its lower stop is the movable contact l5 immediately snaps upwardly. However, there is no lessening of contact pressure between the movable contact l5 and the stationary contact I! until the instant of snap-over.

It is apparent that only a relatively small force is required to actuate the switch and that the parts can be made very light indeed so that they will have an extremely high speed of motion at the instant of snap-over. In the types of switches thus far described, a relatively small force is required to actuate the switch. It is clear that the switch could be constructed so as to require a lesser travel of the actuating member and a larger force to actuate the switch. This type of switch is illustrated in Figures 7 and 8 in which the switch is formed of spring metal, as previously described, but has a pair of outer tension members 24 and a relatively rigid member and a bowed spring member 26. The tension members 24 and the spring member 26 are joined to the rear yoke 21 and the tension members 24 and the relatively rigid member 25 are joined to the front yoke 26. The cantilever spring is indicated as 23 and is located closely adjacent the pivot point of the switch so that only a relatively small motion of the actuating members 30 and is required to operate the switch. The movable contact is indicated by the reference character 32 and the upper stationary contact by the reference character 33 and the lower stationary contact by the reference character 34. The member 25 may be stiffened in any suitable manner; for example, its marginal edges may be turned down as indicated at 35. The relatively rigid member 25 is seated within a notch 36 formed in the single centrally located bearing member 31. The bowed spring member 26 is seated within the rear notch 38 of the bearing member 31.

The operation of this last described form of the invention is the same as that described in connection with the first form of the invention and shown in Figures 1, 2, and 3. In other words, the actuating member 30 or 3| stores energy in the cantilever spring 23. However, there is no lessening of contact pressure between the movable contact 32 and whichever stationary contact it is in engagement with until the forward yoke portion leaves its upper or lower stop 33 or 40, respectively, as previously described. It is clear that this type of switch is not self-restoring. However, it could be made self-restoring if desired by having the relative location of the notches 36 and 38 correspond to those shown in Figures 5 and 6. In the last described form of the invention, the motion of the actuating members may be very small, much smaller than that for the first two forms of the invention. Even in the first two forms of the invention, the switches may be so designed as to require only a small motion of their actuating members.

Referring to Figures 9 and 10 which show a further form of the invention, it will be seen that the same principles are followed as those previously described. In this form of the inven- I tion a pair of bearing members 4| are provided with notches 42 and 43 as previously described. The movable contacts are indicated by the reference character 44 and these movable contacts are carried by the member 45. This member 45 is separate from the member 46 and in this manner differs from the forms of the invention previously described. Each of these members 45 and 46 are rigid and their arms 4! and 48 which seat or pivot within the notches 42 and 43 may be channeled, as indicated, to increase their rigidity. The switch differs in an additional respect from the different forms previously described, in that it is provided with a tension spring 49 joining the members 45 and 46.

The member 46 is limited in its movement by the upper stop portion 50 and the lower stop portion 5| which may be surfaces formed on the member 52. The member 52 and the bearing members 4| are carried by the insulating base member 53. This insulating base member also carries an upper stationary contact 54 and a lower stationary contact 55. A cantilever spring 56 extends outwardly from the member 46 and may be operated in any suitable manner as by means of the upper and lower plungers or members 51 and 58.

It is apparent that when the upper plunger 51, for instance, moves downwardly, that it deflects the spring 56 and stores energy in such' instant of snap-over.

this motion \mtil at the when a suiilcient force is exerted by the spring 56 to move the member 46 downwardly, it is apparent that the member it will snap downwardly and consequently the movable contact 44 will move downwardly and engage the lower contact 55 with a snap action. Obviously when the plunger moves upwardly the reverse action takes place.

While it is believed that the description hereinabove given illustrates the principle of the invention and shows a few of the many forms that it may take, nevertheless it is believed that reference to the work diagram in Figure 11 will be of assistance.

This work diagram is true for all'i'orms oi the invention, but for the sake of simplicity will be described as applied to the first form of the invention as shown in Figures 1, 2, and 3. In this diagram, a force equal to AB must be exerted on the member ID in order to move it away from the upper stop i8. At the instant that the point it snaps from upper stop I8, the force diagram follows the curve BC and it is apparent that this force is of diminishing value until it arrives at the zero point C. The line BC is a slightly curved line due to the increase in bowing of the spring ll during snap action of the switch and would similarly be slightly curved for the corresponding springs of the forms of the invention shown in Figures 4 through 8 and would also similarly be curved due to the slight extension of the spring 49 for the form of the invention shown in Figures 9 and 10. When the point C is arrived at in the force diagram, the movable contact I snaps from its upper to its lower position, whereupon the force necessary to move the point I. changes from C to D. It is apparent that a negative or upward force on the member III has to be exerted of a magnitude corresponding to the line CD before the member It leaves the lower stop l9. At the instant that the switch executes return snap action, it is apparent that the upward or negative force exerted on the member I0 is a decreasing force as indicated by the line DA.

It will be seen that no matter whether the switch is subjected to vibration or not or even if the motion of the actuating member has a vibratory component therein, nevertheless, chatis not lessened durin tering and burning oi! the contacts will not result,

for the contact pressure remains at its maximum value until the instant oi snap-over. At the instant of snap-over, the switch snaps clear over to the other contact as described hereinabove.

It will be seen also that the moving parts of these switches may be made very light indeed and thus an extremely high speed make and break can be obtained.

It is to be noted that contact pressure is not reduced even when the actuating member is moved very slowly as, for example, when the actuation is due to a thermostat.

It is apparent that, although cantilever springs have been shown as the spring means in which energy is stored prior to the snap action of the switch, other types of springs could be used if so desired.

The expression spring or spring means," therefore, is to be interpreted in its ordinary broad meaning unless otherwise specified.

While the switches chosen for illustration have been shown as having spaced stationary contacts, it is obvious that a single contact and a corresponding stop could be employed it so desired.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

We claim:

1. A snap switch comprising a stationary contact, a stationary stop spaced from said stationary contact, a bearing member located between said stop and stationary contact, a movable member having an irmer end provided with a movable contact arranged to coact with said stationary contact and having an outer end arranged to engage said stop when said contacts are in engagement, a tension member connecting said inner and outer ends, means including spring means extending from said outer and inner ends to said bearing member and arranged to place said tension member under tension, energy storing spring means coacting with the outer end 01' said movable member, and operating means arranged tostore energy in said spring means to move said outer end away from said stop to thereby snap said outer end away from said stop and to thereby snap said movable contact away from said stationary contact, whereby there is no lessening of contact pressure up to the instant of snap action.

2. A snap switch comprising a stationary contact, a stationary stop spaced from said station ary contact, a bearing member located between said stop and stationary contact, a movable member having an inner end provided with a movable contact arranged to coact with said stationary contact and having an outer end arranged to engage said stop when said contacts are in engagement, a tension member connecting said inner and outer ends, a rigid member extending from said outer end to said bearing member and a spring member extending from said inner end to said bearing member and arranged to place said tension member under tension, spring means coacting with the outer end of said movable member, and operating means arranged to store energy in said spring means to move said outer end away from said stop with a snap action to thereby snap said movable contact away from said stationary contact, whereby there is no lessening of contact pressure up to the instant of snap action.

3. A snap switch comprising a stationary contact, a first and a second stationary stop opposite each other and spaced from said stationary contact, a bearing member located between said stops and said stationary contact, a movable member having an inner and an outer end, said inner end having a movable contact arranged to engage said stationary contact when said outer end engages said first stop, said movable member including a tension member joining said inner and outer ends, a rigid member extending from one of said ends and a spring member extending from the other of said ends, said rigid member and said spring member engaging said bearing member and being arranged to maintain said tension member in a state of tension, operating means, and an energy storing spring interposed between said operating means and said outer end and arranged to move said outer end from said first stop to said second stop with a snap action, said switch being arranged to have a quick make and quick break without lessening of contact pressure up to the instant of break.

4; A snap switch comprising a movable member formed of spring metal and having an inner .outer end, said ends being Joined by a tension member, a rigid member and a spring member extending towards each other from opposite ends of said movable member, bearing means having notches on opposite sides for the reception of the ends of said rigid'member and said spring member, stationary contact means arranged to coact with said movable contact, a pair of stationary stops on opposite sides of said outer end, a cantilever spring located between said stops and having one end attached to said outer end, and operating means coacting with said cantilever spring to store energy in said cantilever spring, whereby said outer end is snapped from one stop to the other stop and said; movable contact is snapped away from said stationary contact, said switch being characterized by the fact that there is no lessening of contact pressure up to the instant of break, said operating means spaced from said stops and contacting said cantilever spring at a point remote from said stops.

5. A snap action switch comprising stationary contact means, a first rocking member having movable contact means arranged to engage and disengage said stationary contact means, a second rocking member, an energy storing spring member acting upon said second rocking memberand arranged to deflect and store energy for rocking said second rocking member with a snap action, means including over-center spring means connecting said first and said second rocking members and coacting with said first and second rocking members and said energy storing spring member to maintain constant pressure between said contact means until suflicient energy has been stored in said energy storing spring member to rock said rocking members and separate said contacts.

- ANTHONY VAN RYAN.

WILLIAM R. HARRY,

REFERENCES CITED The following references are of record in the 20 file of this patent:

UNITED STATES PATENTS 

